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<title>Calmagite: Description</title>
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<p><b>Calmagite</b> is the common name for
<nobr>1-(1-hydroxy</nobr>-4-methyl-2-phenyl&shy;azo)-2-naphtol-4-sulfonic acid.
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<img src="images/Calgamite.gif" alt="Calgamite structure" title="Calgamite" height="109" width="237" border="1">
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</p>

<p>It was first described in 1960:</p>

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<nobr>F. Lindstrom</nobr> and <nobr>H. Diehl</nobr> (1960) Indicator for the
titration of calcium plus magnesium with (ethyl&shy;ene&shy;dinitrilo)&shy;tetra&shy;acetate,
<i>Anal. <nobr>Chem.</i>,</nobr> <nobr>Vol.32</nobr>, <nobr>pp.1123</nobr>-1127.
</p>

<p>It is normally used in Ca or Mg titrations with <i>edta</i> by adding
5 drops (&#8776;0.25 mL)
of a 0.1% solution (&#8776;2.8 mM). This means that the indicator concentration
in the solution being titrated is somewhere between 3 and 14
<nobr>&times; 10<sup>&#8722;6</sup> M.</nobr> A spectrophotometric procedure is described in:</p>
<p class="indent">
Gordon <i>et al.</i> A micro&shy;scale spectro&shy;photo&shy;metric
determination of water hardness,
<i><nobr>J. Chem.</nobr> Edu.</i> 78 (2001) 1089-1090.
</p>

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